User:Youngsen Jeng

Youngsen Jeng University of Maryland, Baltimore County Undergraduate Student Biological Science

Partnered with Youngdae Kim for a project. University of Maryland, Baltimore County Undergraduate Student Biological Science

Project
Outline of the Project

Glutamine synthetase(GS) is an enzyme that plays an essential role in the metabolism of nitrogen by catalyzing the condensation of glutamate and ammonia to form glutamine. Class I enzymes (GSI) are specific to prokaryotes, and are oligomers of 12 identical subunits The activity of Glutamine Synthetase I-type enzyme is controlled by the adenylation of tyrosine residue

The positively charged monovalent cation contributes to the structural stability of GS. Ginsburg and Stadtman(1973) concluded that dodecameric E. coli Glutamine Synthetase is stabilized by Mn2+, and that monovalent cations stabilize of the quaternary structure of GS. Stabilization by the monovalent cation may be due both to the electrostatic effects of its positive charge and to other components of the energy of the metal-protein bonding. Interactions of the positively charged monovalent cation with the negatively charged substrate glutamate, Glu 212, Ser 53 , and Asp 50 could strengthen the active conformation. Because Ser 53’and Asp 50’reside at the subunit contact surface, the monovalent cation enhances the “side to side” intersubunit interaction.

Structural stabilization of Glutamine Synthetase by divalent cations, especially by the n1 ion, has been ascribed to the attraction of their positive charges to the negative charges of glutamate and ATP and of their ligands (Liaw et al., 1993~).

The structure of the dodecamer exposes several beta loops which are important in stabilizing quaternary structure of Glutamine Synthetase. One beta loop consists of hydrophilic residues 156-173, projects into the central channel of the dodecamer. Another beta loop is the adenylation loop, so called because it contains tyrosyine residue 397 which is covalently modified by addition of AMP.

FINAL PROJECT

Glutamine synthetase(GS) is an enzyme that plays an essential role in the metabolism of nitrogen by catalyzing the condensation of glutamate and ammonia to form glutamine. Glutamine Synthetase I is prokaryotic enzyme and it is consisted of oligomers of 12 identical subunits. The activity of Glutamine Synthetase I-type enzyme is controlled by the adenylation of tyrosine residue.

The positively charged monovalent cation contributes to the structural stability of GS. Ginsburg and Stadtman(1973) concluded that dodecameric E. coli Glutamine Synthetase is stabilized by Mn2+, and that monovalent cations stabilize of the quaternary structure of Glutamine Synthetase. Stabilization by the monovalent cation may be due both to the electrostatic effects of its positive charge and to other components of the energy of the metal-protein bonding. Interactions of the positively charged monovalent cation with the negatively charged substrate glutamate, Glu 212, <scene name='User:Youngsen_Jeng/Ser_53/1'>Ser 53 , and <scene name='User:Youngsen_Jeng/Asp_50/1'>Asp 50 could strengthen the active conformation. Because Ser 53’and Asp 50’reside at the subunit contact surface, the monovalent cation enhances the “side to side” intersubunit interaction.

The structure of the dodecamer exposes several beta loops which are important in stabilizing quaternary structure of Glutamine Synthetase. One beta loop consists of <scene name='User:Youngsen_Jeng/Beta_loop_156-173/1'>hydrophilic residues 156-173, projects into the <scene name='User:Youngsen_Jeng/Beta_loop_projecting/1'>central channel of the dodecamer. Another beta loop is the <scene name='User:Youngsen_Jeng/Beta_loop_with_tyr_397/1'>adenylation loop, so called because it contains tyrosyine residue 397 which is covalently modified by addition of AMP.

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